scripting help with sed

Hi, all!!

I have a sys admin type question.  I'm working with the PR292 final files and have found that we need to do a search/replace in them...  don't get me started, please.

I'm using the following:
sed -e 's/some text/other text/g' < final > output.txt

I'm getting nothing but zero byte files for output.txt does sed have a limitation on line length?  Some of those final files can get upwards of
30,000 characters on one line.  (That is how IL has to have them.)

Other ways to do this? 

Thanks much,
-Greg